<html>
    <body>
        <title></title>
        <form action="loginDo.php" method="post">
            <img src="UseCap.php" alt="" onclick="javascript:this.src='UseCap.php?'+Math.random()"/>
            <input type="text" name="postCode" value="" placeholder="请输入验证码" />
            <input type="submit" name="sb" value="提交">
        </form>
    </body>
</html>